Solar heat collector

ABSTRACT

A solar heat collector includes a trough extending along the ground. The solar heat collector further includes a first region within the trough. The first region extends along a length of the trough. The first region is configured to absorb solar radiation and to heat a fluid flowing within the first region with thermal energy resulting from the absorbed solar radiation. The solar heat collector further includes a second region between the first region and the ground. The second region is substantially thermally insulating the first region from the ground.

CLAIM OF PRIORITY

This application claims the benefit of priority to U.S. Provisional Patent Application No. 60/859,874, filed Nov. 17, 2007, which is incorporated in its entirety by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to solar heat collectors and to solar energy systems utilizing solar heat collectors which use solar radiation to heat a flowing fluid.

2. Description of the Related Art

Flat plate solar heat collector systems (e.g., Thomason's Solaris System) typically utilize a configuration in which water flows down the surface of a corrugated metal surface (e.g., aluminum or galvanized steel). In such systems, a thermal insulation substrate (e.g., polyurethane foam insulation) comprises coolant channels through which water flows and is covered by a glass plate (see, e.g., U.S. Pat. Nos. 3,254,702 and 3,270,739, each of which is incorporated in its entirety by reference herein). Such solar collectors can have widths of about two to four feet and lengths of about ten feet. Such systems have been mounted previously on the roofs of homes or other structures for providing the structure with solar-heated hot water.

Concentrating solar heat collection systems utilize a plurality of reflectors and target receivers having surfaces configured to absorb solar radiation received from the reflectors. For example, the system disclosed by U.S. Pat. No. 6,131,565, which is incorporated in its entirety by reference herein, includes target receivers which are supported by vertical masts above the ground and are oriented to form a linearly extending target. The reflectors are positioned below the target receivers but slightly above ground level and are arrayed to reflect the solar radiation impinging the reflectors towards the target receivers. The reflectors are pivotally mounted and are adjusted to provide synchronized single-axis tracking.

SUMMARY

In certain embodiments, a solar heat collector is provided. The solar heat collector comprises a trough extending along the ground. The solar heat collector further comprises a first region within the trough. The first region extends along a length of the trough. The first region is configured to absorb solar radiation and to heat a fluid flowing within the first region with thermal energy resulting from the absorbed solar radiation. The solar heat collector further comprises a second region between the first region and the ground. The second region is substantially thermally insulating the first region from the ground.

In certain embodiments, a solar heat collection system is provided. The system comprises a fluid distribution conduit. The system further comprises a plurality of solar heat collectors in fluidic communication with the fluid distribution conduit. At least some of the solar heat collectors are generally parallel to one another and spaced from one another to provide an access path for maintenance personnel and equipment to access portions of the solar heat collectors away from a periphery of the solar heat collection system.

In certain embodiments, a solar energy system is provided. The system comprises a fluid distribution conduit. The system further comprises a plurality of solar heat collectors in fluidic communication with the fluid distribution conduit. At least one of the solar heat collectors comprises a trough extending along the ground and is configured to absorb solar radiation and to heat a fluid flowing within the trough. The system further comprises a fluid collection conduit in fluidic communication with the plurality of solar heat collectors. The system further comprises an energy extraction system configured to extract thermal energy from fluid received from the fluid collection conduit. The system further comprises a pumping system configured to receive fluid from the energy extraction system and to pump the fluid to the fluid distribution conduit.

In certain embodiments, a method of heating a fluid is provided. The method comprises providing a trough extending along the ground. The trough comprises a region configured to absorb solar radiation and to have a fluid flowing therethrough such that the fluid is substantially thermally insulated from the ground. The method further comprises flowing the fluid through the region, wherein the fluid is heated with thermal energy resulting from the absorbed solar radiation.

In certain embodiments, a method of generating power is provided. The method comprises providing a plurality of troughs extending along the ground. At least one trough comprises a region configured to absorb solar radiation and to have a fluid flowing therethrough such that the fluid is substantially thermally insulated from the ground. The method further comprises flowing the fluid through the region, wherein the fluid is heated with thermal energy resulting from the absorbed solar radiation. The method further comprises extracting thermal energy from the fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a cross-sectional view of an example solar heat collector compatible with certain embodiments described herein.

FIG. 2 schematically illustrates a cross-sectional view of an example solar heat collector formed in the earth in accordance with certain embodiments described herein.

FIG. 3 schematically illustrates a cross-sectional view of another example solar heat collector compatible with certain embodiments described herein.

FIG. 4 schematically illustrates a cross-sectional view of another example solar heat collector compatible with certain embodiments described herein.

FIG. 5 schematically illustrates a cross-sectional view of another example solar heat collector compatible with certain embodiments described herein.

FIG. 6 schematically illustrates a cross-sectional view of another example solar heat collector compatible with certain embodiments described herein.

FIG. 7 schematically illustrates a perspective cross-sectional view of another example solar heat collector compatible with certain embodiments described herein.

FIG. 8 schematically illustrates an example solar heat collector system compatible with certain embodiments disclosed herein.

FIG. 9 schematically illustrates an example configuration for fluid circulation through a plurality of solar heat collectors in accordance with certain embodiments described herein.

DETAILED DESCRIPTION

Certain embodiments described herein provide a solar heat collector system that generates an output comparable to those of prior art systems and which is advantageously fabricated using low construction costs and operating costs. In certain embodiments, the solar heat collector system utilizes construction materials and ongoing maintenance materials which are relatively inexpensive. In addition, costs are reduced for certain embodiments because relatively unskilled, inexpensive labor can be employed for both the initial construction and the maintenance of the system. As a result, certain embodiments described herein produce electricity at a relatively low cost, with more reliability and less maintenance costs than might be experienced by alternative solar thermal energy systems. In certain embodiments, the solar heat collector system is installed across large areas of land (e.g., desert regions) which are otherwise not utilized. In certain other embodiments, the solar heat collector system is installed on the roofs of large buildings (e.g., warehouses).

FIG. 1 schematically illustrates a cross-sectional view of an example solar heat collector 10 compatible with certain embodiments described herein. The collector 10 comprises a trough 20 extending along the ground 30. The collector 10 further comprises a first region 40 within the trough 20. The first region 40 extends along a length of the trough 20. The first region 40 is configured to absorb solar radiation and to heat a fluid (not shown) flowing within the first region 40 with thermal energy resulting from the absorbed solar radiation. The collector 10 further comprises a second region 50 between the first region 40 and the ground 30. The second region 50 substantially thermally insulates the first region 40 from the ground 30.

In certain embodiments, the fluid flowing through the solar heat collector 10 comprises water, although other fluids can also be used. For example, other fluids compatible with certain embodiments described herein include but are not limited to mixtures of water with ethanol, glycol, salts, or other inorganic materials. In certain embodiments, the fluid comprises water mixed with a material selected to raise the boiling temperature of the mixture above that of water or to lower the freezing temperature of the mixture above that of water. In certain embodiments, the fluid comprises a dye which enhances the absorption of solar radiation by the fluid.

In certain embodiments, the ground 30 along which the trough 20 extends has a grade along at least a portion of the length of the trough 20 such that the portion of the trough 20 is at an incline and the fluid flowing through the portion of the trough 20 flows from a first elevation to a second elevation lower than the first elevation. Thus, in certain such embodiments, flow of the fluid through the trough 20 is facilitated by gravity. In certain other embodiments, the ground 30 along which the trough 20 extends is substantially flat along at least a portion of the length of the trough 20. In certain such embodiments, the fluid is pumped through the trough 20 by a pumping system.

In certain embodiments, the portions of the trough 20 at an incline can be drained by gravity without additional pumping. Certain such embodiments advantageously avoid problems with immobile fluid collecting in flat portions of the trough 20 upon a failure of other portions (e.g., the pumping system) of a solar energy system utilizing the solar heat collector 10. Such immobile fluid is advantageously avoided because it would continue to be heated by solar energy, reaching its boiling temperature and creating pressurized vapor which could damage the solar heat collector 10.

In certain embodiments (e.g., the example solar heat collector 10 of FIG. 1), the trough 20 is formed in the ground 30. In certain other embodiments, the solar heat collector 10 comprises a structural material layer (e.g., concrete) formed along the ground 30, and the trough 20 is formed on or in the structural material layer. For example, in certain embodiments, the trough 20 can be on a platform supported above the ground 30, thereby providing additional thermal insulation between the first region 40 and the ground 30.

FIG. 2 schematically illustrates a cross-sectional view of an example solar heat collector 10 formed in the earth in accordance with certain embodiments described herein. In the example embodiment of FIG. 2, the trough 20 is formed directly in the ground 30 and has a length in a direction generally perpendicular to the cross-sectional view of FIG. 2.

In certain embodiments, the trough 20 has a width in a range between 6 feet and 50 feet. In certain embodiments, the trough 20 has a length in a range between about 500 feet to about 1 mile. While the trough 20 schematically illustrated by FIG. 2 has a generally trapezoidal cross-sectional shape, other cross-sectional shapes (e.g., square, rectangular, curved, irregular) are also compatible with certain embodiments described herein. The cross-sectional shape of the trough 20 in certain embodiments varies along the length of the trough 20. In certain embodiments, the bottom surface of the trough 20 can be flat, curved, or sloped. For example, at an inlet portion of the trough 20, the bottom surface of the trough 20 can be sloped to facilitate fluid flow into the trough 20, and further along the trough 20, the bottom surface can be substantially flat.

In certain embodiments, the first region 40 comprises at least a first layer 42 configured to absorb solar radiation. As used herein, the term “layer” is to be given its broadest ordinary meaning. For example, a layer may comprise a single material having a generally uniform thickness or may comprise multiple adjacent sublayers each comprising a different material. Although many of the layers are depicted herein as having a relatively thin sheet-like expanse or region lying over or under another, a layer as used herein may comprise a shorter expanse or region or multiple expanses or regions.

The first layer 42 of certain embodiments comprises black plastic. As schematically illustrated by FIG. 2, the first layer 42 is configured to support the fluid flowing through the first region 40. The first layer 42 is heated by the absorbed solar radiation and fluid flowing through the first region 40 is heated by the first layer 42. In this way, the fluid flowing within the first region 40 is heated with thermal energy resulting from the absorbed solar radiation. In certain embodiments, the first layer 42 is substantially non-transmissive to infrared radiation, thereby inhibiting heat loss from the fluid. In addition, the first layer 42 is advantageously resistant to degradation from prolonged exposure to ultraviolet radiation.

In certain embodiments, the second region 50 comprises at least a second layer 52 configured to substantially thermally insulate the first region 40 from the ground 30. For example, the second layer 52 of certain embodiments may comprise wood, pressed wood, rubber, foam, polystyrene, polyethylene, and laminate materials. In certain embodiments, the second layer 52 is formed by spraying a material into the trough 20. As schematically illustrated by FIG. 2, the second layer 52 is configured to support the first layer 42. In certain embodiments, the second layer 52 comprises a generally waterproof material which protects other portions of the solar heat collector 10 from exposure to ground moisture.

FIG. 3 schematically illustrates a cross-sectional view of another example solar heat collector 10 compatible with certain embodiments described herein. The second layer 52 of the second region 50 comprises a generally waterproof layer 54 lining an inner surface of the trough 20 and a corrugated layer 56 over the generally waterproof layer 54. At least one or both of the generally waterproof layer 54 and the corrugated layer 56 can comprise plastic. The generally waterproof layer 54 protects other portions of the solar heat collector 10 from exposure to ground moisture and the corrugated layer 56 supports the first layer 42.

FIG. 4 schematically illustrates a cross-sectional view of another example solar heat collector 10 compatible with certain embodiments described herein. Besides the first layer 42, the first region 40 of FIG. 4 further comprises a plurality of supports 44 over the first layer 42 and a third layer 46 over the supports 44. The portion of the first region 40 between the first layer 42 and the third layer 46 forms a conduit 48 through which the fluid can flow. The first layer 42 and the third layer 46 of certain embodiments are substantially impenetrable to water vapor, thereby preventing water vapor from escaping from the first region 40.

In certain embodiments, the supports 44 comprise a plurality of protrusions or dots formed on at least one of the first layer 42 and the third layer 46. The supports 44 maintain the conduit 48 between the first layer 42 and the third layer 46 through which the fluid can flow. In certain embodiments, the supports 44 comprise corrugated material. Materials for the supports 44 in accordance with certain embodiments described herein include, but are not limited to, wood, pressed wood, rubber, foam, polystyrene, polyethylene, and laminate materials.

In certain embodiments, at least one of the first layer 42 and the third layer 46 is substantially absorptive to at least a portion of the solar radiation impinging the first region 40. For example, in certain embodiments, a topmost layer of the first region 40 (e.g., the third layer 46) is configured to be substantially transmissive to at least a portion of the solar radiation impinging on the first region 40, thereby allowing the solar radiation to impinge the flowing fluid and/or the first layer 42 which absorbs solar radiation to heat the fluid. In certain other embodiments, the third layer 46 is configured to absorb solar radiation, thereby heating the fluid with thermal energy resulting from the solar radiation absorbed by the third layer 46. In certain embodiments, a topmost layer of the first region 40 (e.g., the third layer 46) is configured to be substantially non-transmissive to infrared radiation, thereby inhibiting heat loss from the fluid. In addition, the third layer 46 is advantageously resistant to degradation from prolonged exposure to ultraviolet radiation.

FIG. 5 schematically illustrates a cross-sectional view of another example solar heat collector 10 compatible with certain embodiments described herein. The solar heat collector 10 of FIG. 5 comprises a fourth layer 60 (e.g., a top layer) over the third layer 46. The fourth layer 60 of certain embodiments comprises a plastic material that is substantially transmissive to at least a portion of the solar radiation impinging on the fourth layer 60. The third layer 46 and the fourth layer 60 have an air gap therebetween, which in certain embodiments can be maintained by applying a positive pressure to the air between the third layer 46 and the fourth layer 60 (e.g., by an air pump). Solar radiation transmitted through the fourth layer 60 is absorbed by one or more of the third layer 46, the first layer 42, and the fluid, with the absorbed heating the flowing fluid. In certain embodiments, the fourth layer 60 is configured to be substantially non-transmissive to infrared radiation, thereby inhibiting heat loss from the solar heat collector 10. In addition, the fourth layer 60 is advantageously resistant to degradation from prolonged exposure to ultraviolet radiation.

In certain embodiments, the third layer 46 separates the first region 40 from a region 62 above the third layer 46, and the fourth layer 60 separates the region 62 from atmosphere above the fourth layer 60. In certain such embodiments, the region 62 advantageously substantially thermally insulates the first region 40 and the fluid from the atmosphere above the fourth layer 60, thereby reducing heat loss from the fluid. In certain embodiments, the lateral sides of the trough 20 advantageously substantially thermally insulate the first region 40 and the fluid from regions outside a first lateral side of the trough 20 and outside a second lateral side of the trough 20, thereby reducing heat loss from the fluid.

In certain embodiments, the flow of the fluid through the first region 40 (e.g., through the conduit 48 between the first layer 42 and the third layer 46) has a component in a direction substantially along the length of the trough 20. In certain other embodiments, the flow of the fluid also has a component in a direction substantially perpendicular to the length of the trough 20. For example, the flow in certain embodiments is in a serpentine pattern within the trough 20. As another example, the fluid in certain embodiments has motion imparted to it (e.g., by turbulence created in part by the supports 44 or by other means) such that the fluid flows through various portions of the conduit 48 in which it would otherwise not flow (e.g., the upward extending sides of the conduit 48). Certain such embodiments advantageously increase the thermal interaction between the flowing fluid and the layers of the solar heat collector 10 to further heat the fluid.

FIG. 6 schematically illustrates a cross-sectional view of another example solar heat collector 10 compatible with certain embodiments described herein. The trough 20 of certain embodiments is formed in a berm 70, which can comprise an earthen material (e.g., the berm 70 can be formed in the earth), or can comprise other supportive materials including but not limited to asphalt, plastic, or other compositions. In certain embodiments, one or more of the first layer 42, the second layer 52, the third layer 46, and the fourth layer 60 is fastened or held in place by fasteners (e.g., weights) on either side of the trough 20. The sides of the trough 20 are supported by the raised portions of the berm 70 and the various layers of the solar heat collector 10 are fastened to the berm 70. In certain embodiments, the fasteners are configured to be replaceable on a scheduled or emergency basis, with minimal effort and cost. In certain embodiments, the weights have a “V”-shaped cross-sectional shape. In certain embodiments, the trough 20 has a depth in a range between about 0.5 foot to about 2.5 feet (e.g., about 1.5 feet), and the air gap between the third layer 46 and the fourth layer 60 has a depth in a range between about 0.5 foot to about 2 feet (e.g., about 1 foot).

FIG. 7 schematically illustrates a perspective cross-sectional view of another example solar heat collector 10 compatible with certain embodiments described herein. In the second region 50, the trough 20 comprises an insulating layer of large rocks, medium rocks, and sand at the bottom of the trough 20. In the first region 40, the trough 20 comprises rocks 80 which space apart two layers 82, 84 (e.g., plastic) which form the conduit 48 through which the fluid flows. In certain embodiments, a plurality of rocks 90 are placed above the conduit 48 to weigh down the uppermost layer 84 (e.g., to prevent wind from displacing the layer 84). In certain embodiments, the width of the trough 20 is about 30 feet, and the depth of the trough 20 is about 18 inches, while in certain other embodiments, other dimensions as described herein are used.

In certain embodiments, the solar heat collector 10 is designed for simplicity of fabrication and maintenance or repair. For example, in certain embodiments, plastic layers used for the solar heat collector 10 can be unrolled from large industrial-sized rolls, and any insulating materials can be prefabricated and delivered to the site where the solar heat collector 10 is to be installed. In certain embodiments, a mobile machine that is configured to fabricate and/or repair the solar heat collector 10 may be used. In certain embodiments, a mobile vacuum unit is used as part of an ongoing maintenance program to remove dust from the top surface of the solar heat collector 10 which would otherwise inhibit solar radiation from reaching the first region 40. An example vacuum unit can travel at about five miles per hour and collect dust from the top surface of the solar heat collector 10 at about 100 hours per square mile, for ten-foot-wide troughs 20.

FIG. 8 schematically illustrates a solar heat collection system 100 compatible with certain embodiments described herein. The system 100 comprises a fluid distribution conduit 110 and a plurality of solar heat collectors 120 in fluidic communication with the fluid distribution conduit 110. At least some of the solar heat collectors 120 are generally parallel to one another and spaced from one another to provide an access path to provide access for maintenance personnel and equipment to portions of the solar heat collectors 120 away from the periphery of the system 100. At least some of the solar heat collectors 120 are coupled to the fluid distribution conduit 110 in parallel to one another by one or more adjustable valves 130.

In certain embodiments, the fluid distribution conduit 110 has a drop of about 40 feet per linear mile, and a length of about 1 mile to about 2 miles.

In certain embodiments, as schematically illustrated by FIG. 8, at least one of the solar heat collectors 120 comprises a plurality of solar heat collector segments 122 which are in serial fluidic communication with one another such that fluid flows from one segment 122 to the next. Examples of solar heat collector segments 122 compatible with certain embodiments described herein are described herein in conjunction with FIGS. 1-7. The solar heat collector segments of certain embodiments have a width in a range between about 20 feet to about 50 feet (e.g., about 30 feet) and include one or more troughs having solar-radiation-absorbing regions through which the fluid (e.g., water) flows and is heated. In certain embodiments, the solar heat collectors 120 are positioned along a graded portion of the ground 30 such that gravity facilitates the flow of fluid from the fluid distribution conduit 110 at one end of the solar heat collector 120 to a lower end of the solar heat collector 120.

In certain embodiments, one end of one segment 122 overlaps another end of a subsequent segment 122. In certain embodiments, the solar heat collectors 120 are generally parallel to one another and are spaced by about 3 feet from one another, while in certain other embodiments, the spacing between generally parallel solar heat collectors 120 is in a range between about 2 feet to about 10 feet. These spacings between the generally parallel solar heat collectors 120 advantageously provide one or more access paths or service lanes which allow personnel and equipment to access portions of the solar heat collectors 120 away from a periphery of the solar heat collection system 100 for initial fabrication and for scheduled or unscheduled maintenance. Certain embodiments further comprise additional service lanes extending generally perpendicularly to the solar heat collectors 120 to provide additional ease of transporting personnel, equipment, and/or materials across the expanse of the solar heat collector system 100. In certain embodiments, the solar heat collectors 120 have a length in a range between about 0.5 mile to about 1 mile, and the solar heat collector system 100 has a width in a range between about 0.5 mile to about 1 mile (excluding the widths of the service lanes between the solar heat collectors 120).

In certain embodiments, each valve 130 is in fluidic communication with a corresponding port from the fluid distribution conduit 110, and the valve 130 is configured to controllably adjust the amount of fluid flowing from the fluid distribution conduit 110 into the corresponding solar heat collector 120. In certain embodiments, the valves 130 comprise all the moving parts of the solar heat collection system 100.

Certain embodiments further comprise a network of measurement devices placed at selected locations within the solar heat collection system 100 and a computer system (e.g., microprocessor) operatively coupled to the valves 130 and to the network of measurement devices. The computer system is configured to receive input signals from the network and to transmit output signals to the valves, and the valves are responsive to the output signals to controllably adjust fluid flow through the plurality of solar heat collectors. The computer system of certain embodiments is configured to receive input from personnel and from sensors positioned along the solar heat collection system 100. In certain embodiments, the network of measurement devices is for various purposes. For example, a plurality of temperature sensors can be used to monitor and control the local temperature of the flowing fluid. Other sensors can be used to provide an alert signal indicative of an unanticipated situation or condition within the solar heat collector system 100.

In certain embodiments, the solar heat collection system 100 is stationary with no moving parts (with the exception of the valves 130) which affect the absorption of solar radiation by the system 100. Optimization of the system 100 for a given geographical area will be dependent upon optimizing the collector materials and dimensions, determining the orientation of the system 100 (e.g., with respect to true north), the slope of the solar heat collectors 120 along the ground 30, the distribution and flow of fluid (e.g., water) within the system 100, and the timing of the heated fluid flowing through the system 100. For example, during early morning and late afternoon hours, the solar heat collection system 100 may sustain a certain amount of radiation blockage due to shadows caused by the sides of the solar heat collectors 120. The anticipated amount of such radiation blockage can be used in determining the directional orientation of the solar heat collection system 100. For example, in certain embodiments, the troughs 20 are laid out to extend east-to-west, thereby minimizing the shadows of the berms 70 or other structures extending across the irradiated surface of the solar heat collectors 120. In certain embodiments, the process of optimization advantageously (i) achieves the highest total efficiency of the system, and therefore the maximum electricity output per day or per year; (ii) minimizes the cost of construction of the total system while maximizing the lifetime of its components; or (iii) minimizes ongoing maintenance costs while not jeopardizing the integrity of the system.

FIG. 9 schematically illustrates an example configuration for fluid circulation through a solar energy system 130 comprising a solar heat collector system 100 with a plurality of solar heat collectors 120 in accordance with certain embodiments described herein. Fluid flow through the solar energy system 130 is denoted by arrows in FIG. 9. In certain embodiments, fluid (e.g., water) at an initial temperature of about 70 degrees Fahrenheit flows into the plurality of solar heat collectors 120 via the fluid distribution conduit 110 at a first elevation. The fluid is heated as it flows through the solar heat collectors 120, reaching a final temperature in a range between about 120 degrees Fahrenheit to about 270 degrees Fahrenheit (e.g., a temperature of about 145 degrees Fahrenheit or a temperature of about 165 degrees Fahrenheit) at a second elevation lower than the first elevation. The heated fluid from the solar heat collectors 120 is collected in a fluid collection conduit 135 and flows to an energy extraction system 140 (e.g., a working-fluid-driven system, a turbine system, or a low-temperature Rankine cycle power plant), which extracts the heat from the heated fluid (e.g., by producing electricity) such that the fluid is cooled. The now-cooled fluid is then pumped back to the first elevation to the fluid distribution conduit 110 by the pumping system 150.

In certain embodiments, the solar energy system 130 is entirely driven by solar energy, with the possible exception of the pumps, lights, etc. In certain other embodiments, the solar energy system 130 further comprises an additional power generating booster unit (e.g., a gas boiler) between the solar heat collector system 100 and the energy extraction system 140. In certain such embodiments, this booster unit can advantageously be used to increase the temperature of the fluid emerging from the solar heat collection system 100 (e.g., beyond the boiling point of the fluid) in order to increase the efficiency of the energy extraction system 140.

In certain embodiments, the energy extraction system 140 has certain operating parameters, such as suggested or required incoming fluid temperature and volume of incoming fluid flow per minute. At any one time, fluid emerging from the solar heat collector system 100 may be stored in a fluid storage system, may be run into the energy extraction system 140, or may be run back into the solar heat collector system 100 to gather more heat. For example, heated fluid from the solar heat collector system 100 can be collected and pumped into a first storage system prior to being pumped into the energy extraction system 140. Fluid from this first storage system in certain embodiments can be selectively diverted to the energy extraction system 140 or can be pumped back to the solar heat collector system 100 to be further heated. In certain embodiments, fluid emerging from the energy extraction system 140 is pumped into a second storage system. In certain such embodiments, fluid from either the first storage system or the second storage system is selectively pumped into the solar heat collectors 120 via the fluid distribution conduit 110. The computerized control system of certain embodiments can be programmed to optimize the system performance by determining which of these options will maximize electricity output on a continuous basis.

In certain embodiments, the solar energy system 130 can also be optimized in terms of the relative electric power output of the solar heat collector system 100 versus the input power requirements of the energy extraction system 140. Thus, for a specific maximum power output of the energy extraction system 140, the size of the solar heat collector system 100 can be increased such that more energy is stored in the heated fluid, and therefore the solar energy system 130 may continue to provide electricity for a longer period of time during a given one-day or several-day period.

Various embodiments have been described above. Although the invention has been described with reference to these specific embodiments, the descriptions are intended to be illustrative of the invention and are not intended to be limiting. Various modifications and applications may occur to those skilled in the art without departing from the true spirit and scope of the invention as defined in the appended claims. 

1. A solar heat collector comprising: a trough extending along the ground; a first region within the trough, the first region extending along a length of the trough, the first region configured to absorb solar radiation and to heat a fluid flowing within the first region with thermal energy resulting from the absorbed solar radiation; and a second region between the first region and the ground, the second region substantially thermally insulating the first region from the ground
 2. The solar heat collector of claim 1, wherein the ground along which the trough extends has a grade along at least a portion of the length of the trough such that fluid flowing through the portion of the trough flows from a first elevation to a second elevation lower than the first elevation.
 3. The solar heat collector of claim 1, wherein the ground along which the trough extends is substantially flat along at least a portion of the length of the trough.
 4. The solar heat collector of claim 1, wherein the trough is on or in the ground.
 5. The solar heat collector of claim 1, further comprising a structural material layer formed along the ground, the trough formed on or in the structural material layer.
 6. The solar heat collector of claim 1, wherein the trough has a width in a range between 6 feet and 50 feet and a length in a range between about 500 feet and 1 mile.
 7. The solar heat collector of claim 1, wherein the first region comprises at least a first layer configured to absorb solar radiation, the first layer configured to support fluid flowing through the first region.
 8. The solar heat collector of claim 1, wherein the second region comprises at least a second layer configured to substantially thermally insulate the first region from the ground and to support the first layer.
 9. The solar heat collector of claim 8, wherein the second layer comprises a generally waterproof layer.
 10. The solar heat collector of claim 9, wherein the second layer further comprises a corrugated layer over the generally waterproof layer.
 11. The solar heat collector of claim 1, wherein the second region comprises rocks and sand.
 12. The solar heat collector of claim 1, wherein the first region comprises at least two layers and a plurality of supports therebetween, thereby forming a conduit through which fluid can flow.
 13. The solar heat collector of claim 12, wherein the supports comprise a plurality of protrusions formed on at least one of the two layers.
 14. The solar heat collector of claim 12, wherein the supports comprise a plurality of rocks.
 15. The solar heat collector of claim 12, wherein at least one of the two layers is substantially absorptive to at least a portion of the solar radiation impinging the first region.
 16. The solar heat collector of claim 15, wherein a topmost layer of the two layers is substantially non-transmissive to infrared radiation.
 17. The solar heat collector of claim 12, further comprising a top layer above the at least two layers with an air gap between the top layer and the at least two layers.
 18. The solar heat collector of claim 17, wherein the top layer is substantially transmissive to at least a portion of the solar radiation impinging the top layer and is substantially non-transmissive to infrared radiation.
 19. The solar heat collector of claim 17, wherein the air gap has a positive pressure.
 20. The solar heat collector of claim 1, wherein flow of fluid through the first region has a component in a direction substantially along the length of the trough and a component in a direction substantially perpendicular to the length of the trough.
 21. The solar heat collector of claim 1, wherein the trough is formed in a berm.
 22. A solar heat collection system comprising: a fluid distribution conduit; and a plurality of solar heat collectors in fluidic communication with the fluid distribution conduit, at least some of the solar heat collectors generally parallel to one another and spaced from one another to provide an access path for maintenance personnel and equipment to access portions of the solar heat collectors away from a periphery of the solar heat collection system.
 23. The solar heat collection system of claim 22, further comprising one or more adjustable valves in fluidic communication with the fluid distribution conduit and with one or more of the solar heat collectors.
 24. The solar heat collection system of claim 22, wherein at least some of the solar beat collectors are coupled to the fluid distribution conduit in parallel to one another.
 25. The solar heat collection system of claim 22, wherein at least one of the solar heat collectors comprises a plurality of solar heat collector segments which are in serial fluidic communication with one another such that fluid flows from one segment to the next.
 26. The solar heat collection system of claim 22, further comprising a network of measurement devices placed at selected locations within the solar heat collection system and a computer system operatively coupled to the valves and to the network of measurement devices, the computer system configured to receive input signals from the network and to transmit output signals to the valves, the valves responsive to the output signals to controllably adjust fluid flow through the plurality of solar heat collectors.
 27. A solar energy system comprising: a fluid distribution conduit; a plurality of solar heat collectors in fluidic communication with the fluid distribution conduit, at least one of the solar heat collectors comprising a trough extending along the ground and configured to absorb solar radiation and to heat a fluid flowing within the trough; a fluid collection conduit in fluidic communication with the plurality of solar heat collectors; an energy extraction system configured to extract thermal energy from fluid received from the fluid collection conduit; and a pumping system configured to receive fluid from the energy extraction system and to pump the fluid to the fluid distribution conduit.
 28. The solar energy system of claim 27, wherein the energy extraction system comprises a low-temperature Rankine cycle power plant.
 29. A method of heating a fluid, the method comprising: providing a trough extending along the ground, the trough comprising a region configured to absorb solar radiation and to have a fluid flowing therethrough such that the fluid is substantially thermally insulated from the ground; and flowing the fluid through the region, wherein the fluid is heated with thermal energy resulting from the absorbed solar radiation.
 30. The method of claim 29, wherein the trough comprises at least one layer above the region, the at least one layer separating the region from atmosphere above the layer, the fluid substantially thermally insulated from the atmosphere above the layer.
 31. The method of claim 29, wherein the fluid is substantially thermally insulated from regions outside a first lateral side of the trough and outside a second lateral side of the trough.
 32. A method of generating power, the method comprising: providing a plurality of troughs extending along the ground, at least one trough comprising a region configured to absorb solar radiation and to have a fluid flowing therethrough such that the fluid is substantially thermally insulated from the ground; flowing the fluid through the region, wherein the fluid is heated with thermal energy resulting from the absorbed solar radiation; and extracting thermal energy from the fluid. 